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Snow processes in ORCHIDEE

Snow processes in ORCHIDEE. Tao Wang, C. Ottlé, P. Ciais, etc. Snow roles in high latitudes:. Thicker snow, warmer soil temp. Less snow, warmer air temperatures. Prolonged snow, later vegetation greening. earlier snowmelt, earlier spring runoff. NDVI. (30 May - 5 June).

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Snow processes in ORCHIDEE

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  1. Snow processes in ORCHIDEE Tao Wang, C. Ottlé, P. Ciais, etc..

  2. Snow roles in high latitudes: Thicker snow, warmer soil temp. Less snow, warmer air temperatures Prolonged snow, later vegetation greening earlier snowmelt, earlier spring runoff NDVI (30 May - 5 June)

  3. ORCHIDEE Snow developments • Single layer vs. Three layers • Composite vs. Separate snow structure • Snow density and snow thermal conductivity (constant vs. variable) • Freezing and refreezing processes (no vs. yes) • Water flow between layers (no vs. yes) Old ORCHIDEE (ORC-O, 1-layer) New ORCHIDEE (ORC-ES, 3-layers) Heat Water Heat Water Kin Lin Kin Lin H LE Qp P En En H LE P Tsurf Skin layer J J1 K1 Q1, T1, D1, ρ1 P1 Ws1, Wl1, D1, ρ1 Q2, T2, D2, ρ2 Ws2, Wl2, D2, ρ2 J2 K2 P2 Tsurf > 0, snow melt occurs; Ws, D, ρ T, D, ρ Q3, T3, D3, ρ3 Ws3, Wl3, D3, ρ3 J3 K3 P3 Separate Separate composite composite Top soil layer Top soil layer Top soil layer Top soil layer 3

  4. Sensitivity tests (Morris method) ORCHIDEE-ES on Col de Porte Albedo-related Most important Very important for soil temperature simulation Thermal conductivity-related Very important for snow depth simulation Snow compaction factors

  5. Evaluation results (CDP-snow depth)

  6. Evaluation results (Albedo and soil temperature), Col de Porte, mean seasonal cycle (1993-2011)

  7. How to constrain snow albedo feedback in model ? Option 1: Developing physical-based snow albedo scheme taking into account snow grain size, impurity content etc Albedo = f(snow age) Albedo = f(snow grain size, impurity, sun angle, snow depth)

  8. How to constrain snow albedo feedback in model ? Option 1: Developing physical-based snow albedo scheme taking into account snow grain size, impurity content etc Option 2: Data assimilation fromin-situ or albedo product (GlobAlbedo) In-situ snow albedo assimilation into ORCHIDEE-ES (alpine site, WFJ)

  9. How to constrain snow albedo feedback in model ? Option 1: Developing physical-based snow albedo scheme taking into account snow grain size, impurity content etc Option 2: Data assimilation fromin-situor albedo product (GlobAlbedo) April Reflected radiation (albedo x SWdown) Control Assimil. Wang et al. (in preparation)

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